The present invention relates to printing and, more particularly, to printing other than lithography, letterpress and gravure.
The conventional printing techniques such as lithography, letterpress and gravure require the use of a plate which is prepared with inked areas forming the image to be printed. More recently, there have been developed various ink jet printing systems which generally involve the directing of ink particles from jet nozzles and the selective application or deposition of such ink particles onto a print medium. These ink jet printing systems, while providing many desirable advantages over other print techniques, are, however, not suitable for simultaneous multiple copy applications.
U.S. Pat. No. 3,790,703 to Carley discloses a printing system in which a fluid stream is thermal viscosity modulated by time varying the temperature of the stream in response to an intelligence signal. The thermal viscosity modulation of the fluid stream is accomplished by passing a plurality of fluid ink streams under pressure through capillary tubes having thin film resistors on their walls, and impressing the scanned original electrical signals through the resistors to selectively heat the fluid ink stream. The thermally produced variations in the viscosity of the fluid ink stream correspondingly alter the ink flow through the capillary tubes. Electrostatic ink transfer techniques may also be employed with the disclosed thermal viscosity modulation system. The use of thermal viscosity modulation is dependent on thermal conductivity with its inherent thermal spreading problems, which may affect the quality and resolution of the print. Also, it is generally only capable of single copy printing.
U.S. Pat. No. 3,270,637 to H. E. Clark discloses a printing system which utilizes an electro-viscous liquid. In response to the application of a writing signal, such as an applied voltage, the liquid increases in viscosity and the system does not print. Conversely, in the absence of an applied signal the viscosity of the liquid decreases and the system prints. Other forms of energy such as light, etc., may be used as the energizing signal for controlling the viscosity of the electro-viscous liquid.
U.S. Pat. No. 3,369,253 to Sihvonen discloses a printing system in which a normally solid non-aqueous ink is heated, with the liquified ink being used for printing purpose.